Significant advances in industrial process control technology have vastly improved all aspects of factory and plant operation. Before the introduction of today's modern industrial process control systems, industrial processes were operated/controlled by humans and rudimentary mechanical controls. As a consequence, the complexity and degree of control over a process was limited by the speed with which one or more people could ascertain a present status of various process state variables, compare the current status to a desired operating level, calculate a corrective action (if needed), and implement a change to a control point to affect a change to a state variable.
Improvements to process control technology have enabled vastly larger and more complex industrial processes to be controlled via programmed control processors. Control processors execute control programs that read process status variables and execute control algorithms based upon the status variable data and desired set point information to render output values for the control points in industrial processes. Such control processors and programs support a substantially self-running industrial process (once set points are established).
Notwithstanding the ability of industrial processes to operate under the control of programmed process controllers at previously established set points without intervention, supervisory control and monitoring of control processors and their associated processes are desirable. Such oversight is provided by both humans and higher-level control programs at an application/human interface layer of a multilevel process control network. Such oversight is generally desired to verify proper execution of the controlled process under the lower-level process controllers and to configure the set points of the controlled process.
Various data input/output servers, including for example data access servers, facilitate placing process control data (both reading and writing) within reach of a variety of higher-level monitor/control client applications. During the course of operation, process controllers generate status and control information concerning associated processes. The controllers' process status and control information is stored within process control databases and/or distributed to a number of locations within the process control network. Other process information is generated/stored within field devices (e.g., intelligent transmitters) having digital data communication capabilities. The process information is retrieved from the process control databases and field devices by data access servers for further processing/use by the process control system. For example, the data access servers provide the retrieved information to a variety of client applications providing high-level control and monitoring (both human and computerized) services.
In systems containing data input/output servers, the high-level control and monitoring applications rely upon the proper operation of the servers to provide the data upon which such applications rely for decision-making. The information includes real-time process variable values, alarms, etc. Data input/output servers are implemented in a number of forms. In some systems, a single data access server operates upon a single node on a computer network from which higher level supervisory control is implemented. In other systems, multiple data access servers are located upon a local area network, and the multiple data access servers are accessed by supervisory-level applications running on other nodes on a local control network. In yet other systems, access to process control information/resources is achieved via temporary sessions established via a wide area network link. One particular example is data access provided via an Internet/intranet portal server.
A portal site is an Internet/intranet site that provides access to a variety of information from potentially many sources. Portal sites, referred to as vertical portals, are sometimes designed to provide access to a particular type of information. Portal servers handle user traffic at portal sites and provide user access over the Internet/intranet to the variety of data sources exposed by the portal site. Such users generally access the portal site via remote computers executing general browser software such as the well known MICROSOFT INTERNET EXPLORER or NETSCAPE NAVIGATOR. Through the browsers the users access the data sources exposed by the portal site/server.
Portal servers provide a wide variety of services. One example of such a service is “content accessibility” that facilitates connectivity to information sources and/or content providers. Content includes: online documents, libraries, databases, and government. Such content can be located over a wide geographic area, but is connected via a network structure (e.g., the Internet). Another example of a portal service is a search engine that enables users to locate particular information within a vast amount of available content. A portal server often maintains an index to enhance performance of searches. Another portal service is visualization of available services (e.g., displaying various features available to users). A second aspect to visualization is displaying documents and information retrieved at the request of a user. Yet another portal server function is providing access to users from many parts of the world via the World Wide Web. Such access includes both domestic and foreign users. A last example of a portal function is support for personalization. A portal is used by many different people for many purposes. Portal servers store user profile information to enhance user experiences.
An advantage of a portal server approach to accessing process control information/resources is the ability of users to gain access from virtually any location in the world. Such access enables specialists (both human and programmed) to obtain access to and provide supervisory services without having to be physically present on the manufacturing/industrial plant. Such accessibility can save an enterprise considerable time and costs and avoid travel delays. Wide area network access of the type supported by a portal server also enables centralized, coordinated, and highly integrated control of an enterprise spread over a relatively wide geographic area. Notwithstanding the significant benefits of providing Web access to a process control network, significant challenges are faced with regard to regulating access to the process control network information and resources as well as to properly charging customers for their use of such portal services.